The present invention relates to an apparatus for controlling a vehicular transmission, and more particularly to an apparatus for controlling a transmission actuator associated with a transmission having a synchromesh.
There have been developed in recent years electronically controlled automatic vehicular transmissions employing microcomputers.
Transmission actuators for actuating such automatic transmissions are generally hydraulically operated actuators.
Where a hydraulic transmission actuator is employed, a hydraulic pressure generating device is required to supply a hydraulic pressure for operating the hydraulic transmission actuator. There are also required a hydraulic circuit for connecting the hydraulic pressure generating device and the actuator, and a control valve and other components for controlling the hydraulic pressure to be supplied to the actuator. The overall transmission actuator system is large in size, heavy in weight, and costly to manufacture.
One transmission actuator proposed to eliminate the aforesaid problems employs an electric motor.
The transmission actuator employing an electric motor comprises the electric motor, a speed reducer for reducing the speed of rotation of the electric motor, and a transmission mechanism for converting the rotary motion from the speed motor into linear motion.
A transmission actuator for actuating a transmission having a synchromesh, particularly a shifting actuator, has a shifting stroke including a synchromesh region and a non-synchromesh region subsequent to synchromesh operation. A load in shifting operation within the synchromesh region (synchromesh load) is large as compared with the load required in the non-synchromesh region, and therefore a large thrust is necessary in the synchromesh region. If the actuator is operated in the non-synchromesh region while the large thrust remains to be applied, unnecessary forces would be imposed on the gears of the transmission, giving off impact sounds and lowering the durability and reliability of the components of the transmission.
One solution disclosed in Japanese Laid-Open Patent Publication No. 58-134256 includes a damping spring device mounted on a rod for operating a shifting lever, the rod being linearly movable by a transmission mechanism in a motor actuator.
Since the disclosed arrangement employs a damping spring device, however, the structure of the actuator is complex.